Optogenetic control of the Bicoid morphogen reveals fast and slow modes of gap gene regulation
Anand P. Singh,
Ping Wu,
Sergey Ryabichko,
João Raimundo,
Michael Swan,
Eric Wieschaus,
Thomas Gregor,
Jared E. Toettcher
Affiliations
Anand P. Singh
Lewis Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA
Ping Wu
Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
Sergey Ryabichko
Lewis Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA
João Raimundo
Lewis Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA
Michael Swan
Lewis Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA; Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
Eric Wieschaus
Lewis Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA; Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA; Corresponding author
Thomas Gregor
Lewis Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA; Department of Physics, Princeton University, Princeton, NJ 08544, USA; Corresponding author
Jared E. Toettcher
Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA; Corresponding author
Summary: Developmental patterning networks are regulated by multiple inputs and feedback connections that rapidly reshape gene expression, limiting the information that can be gained solely from slow genetic perturbations. Here we show that fast optogenetic stimuli, real-time transcriptional reporters, and a simplified genetic background can be combined to reveal the kinetics of gene expression downstream of a developmental transcription factor in vivo. We engineer light-controlled versions of the Bicoid transcription factor and study their effects on downstream gap genes in embryos. Our results recapitulate known relationships, including rapid Bicoid-dependent transcription of giant and hunchback and delayed repression of Krüppel. In addition, we find that the posterior pattern of knirps exhibits a quick but inverted response to Bicoid perturbation, suggesting a noncanonical role for Bicoid in directly suppressing knirps transcription. Acute modulation of transcription factor concentration while recording output gene activity represents a powerful approach for studying developmental gene networks in vivo.
